The bypass duct of a turbofan gas turbine engine contains a pressurized flow of air between the outer duct wall and the engine core. At several locations along the length and about the circumference of the annular bypass duct, penetrations are necessary for conveying fuel, oil, control cables or compressed air bleed from the compressor to an aircraft cabin, as well as many control and monitoring penetrations for instrumentation, inspection and maintenance.
In the prior art, penetrations through the bypass duct are generally accomplished by shrouding the conduits or cables in a transverse sheet metal projection that may be contoured for improved aerodynamic properties. The intersection between the transverse sheet metal projection and the sheet metal walls of the bypass duct are generally manufactured with a flange that is riveted or faulted to the relatively thin sheet metal bypass duct walls. Such connections however must also accommodate the difference in pressure between the pressurized flow of air through the bypass duct and the ambient air surrounding the exterior of the engine. Further, the engine core and the associated inner bypass duct wall are exposed to significant heat and thermal expansion and contraction relative to the less exposed outer bypass wall. As a result, relative thermal expansion and contraction is also accommodated by the connection between the projection and the outer bypass wall or the inner bypass wall depending on the particular arrangement.
As a result of the pressure differential and need to accommodate relative thermal expansion and contraction, the sealing and mechanical connection between projections through the bypass wall and the relatively thin bypass duct walls is a relatively complex arrangement requiring clearance for expansion and contraction, resilient seals and quite often involves riveting a structural support or containment flange to the relatively thin bypass duct walls surrounding the opening for the penetration.
It is an object of the invention to provide a means to seal between the opening and the gas turbine engine bypass duct wall and the external surface of a projection extending through the opening which accommodates relative thermal expansion and contraction and pressure differential in a simple low cost manner.
Further objects of the invention will be apparent from review of the disclosure, drawings and description of the invention below.